In turn ace goes wrong, lacking confidence (9)
I believe the answer is:
uncertain
'lacking confidence' is the definition.
(I've seen this before)
'in turn ace goes wrong' is the wordplay.
'goes wrong' indicates an anagram.
'in'+'turn'+'ace'='inturnace'
'inturnace' with letters rearranged gives 'UNCERTAIN'.
(Other definitions for uncertain that I've seen before include "In doubt" , "up in the air" , "Doubtful, indecisive" , "dubious" , "Not definitely known" .)